"The Duke of Cambridge is honoured to have been asked, and is very much looking forward to supporting his brother at St George's Chapel, Windsor on May 19th," Kensington Palace said.

Earlier this week William and Kate, whose official titles are the Duke and Duchess of Cambridge, celebrated the arrival of their third child.

The role means William, whose official title is the Duke of Cambridge, will miss English soccer's FA Cup final as it clashes with the wedding, media reported. William, as President of the Football Association, usually awards the trophy to the winners.